TERRESTRIAL LASER SCANNING SPECIFICATIONS • June 2018 15 Terrestrial Laser Scanning Specifications Table of Contents 15 Terrestrial Laser Scanning Specifications................................................................. 1 15 Terrestrial Laser Scanning...................................................................................... 3 15.1 Stationary Terrestrial Laser ................................................................................... 5 15.2 STLS Applications ................................................................................................... 7 15.2-1 Type A - Hard surface topographic surveys: .................................................. 7 15.2-2 Type B - Earthwork and lower-accuracy topographic surveys: ...................... 7 15.3 STLS Project Selection ............................................................................................ 9 15.4 STLS Equipment and Use ..................................................................................... 11 15.4-1 Eye Safety ..................................................................................................... 11 15.4-2 Useful Range of Scanner............................................................................... 11 15.4-3 Scanner Targets............................................................................................. 11 15.5 STLS Specifications and Procedures.................................................................... 13 15.5-1 Planning ......................................................................................................... 13 15.5-2 Project Control Establishment and Target Placement................................... 14 15.5-3 Equipment Set-up and Calibration ................................................................ 14 15.5-4 Redundancy ................................................................................................... 15 15.5-5 Monitoring STLS Operation ......................................................................... 15 15.5-6 Quality Control .............................................................................................. 15 15.6 STLS Deliverables and Documentation ............................................................... 17 15.6-1 STLS Deliverables ........................................................................................ 17 15.6-2 STLS Documentation .................................................................................... 17 Table 15-1 Stationary Terrestrial Laser Scanning Specifications................................... 19 15.7 Mobile Terrestrial Laser Scanning....................................................................... 21 15.8 MTLS Applications ................................................................................................ 23 15.8-1 Type A - Hard surface topographic surveys: ................................................ 23 15.8-2 Type B - Earthwork and low-accuracy topographic surveys:....................... 23 15.9 MTLS Project Selection......................................................................................... 25 15.10 MTLS Equipment and Use.................................................................................... 27 15.10-1 Eye Safety ..................................................................................................... 27 15.10-2 Useful Range of MTLS system..................................................................... 27 15.10-3 Local registration and Validation Points ....................................................... 27 15.11 MTLS Specifications and Procedures .................................................................. 29 15.11-1 Mission Planning ........................................................................................... 29 15.11-2 GNSS Project Control ................................................................................... 29 15.11-3 Equipment Calibration .................................................................................. 30 15.11-4 Redundancy ................................................................................................... 30 © 2018 California Department of Transportation CALTRANS • SURVEYS MANUAL 15-1 TERRESTRIAL LASER SCANNING SPECIFICATIONS • June 2018 15.11-5 Monitoring Equipment during Data Collection ............................................ 30 15.11-6 Local Registration and Validation Requirements ......................................... 30 15.11-7 Quality Control .............................................................................................. 32 15.12 MTLS Deliverables and Documentation.............................................................. 34 15.12-1 MTLS Documentation................................................................................... 34 Table 15-2 Mobile Terrestrial Laser Scanning Specifications ....................................... 36 Table 15-2 Mobile Terrestrial Scanning Specifications - Continued ............................. 37 Appendix 15A: Glossary................................................................................................... 38 Appendix 15B: STLS Checklist ....................................................................................... 40 Appendix 15C: MTLS Checklist ..................................................................................... 41 © 2018 California Department of Transportation CALTRANS • SURVEYS MANUAL 15-2 TERRESTRIAL LASER SCANNING SPECIFICATIONS • June 2018 15 Terrestrial Laser Scanning Laser scanning or Light Detection and Ranging (LiDAR) systems use lasers to make measurements from a tripod or other stationary mount, a mobile mapping vehicle, or an aircraft. The term LiDAR is sometimes used interchangeably with laser scanning . Terrestrial LiDAR or Terrestrial Laser Scanning (TLS) as discussed in this chapter does not pertain to airborne LiDAR or Airborne Laser Scanning (ALS), which will be addressed in a revision of the Caltrans Surveys Manual (CSM), Chapter 13, Photogrammetry. Survey specifications describe the methods and procedures needed to attain a desired survey accuracy standard. For complete accuracy standards, refer to CSM Chapter 51, “Classifications of Accuracy and Standards.” Caltrans survey specifications shall be used for all Caltrans-involved transportation improvement projects, including special-funded projects. 1 http://www.dot.ca.gov/hq/row/landsurveys/SurveysManual/05_Surveys.pdf © 2018 California Department of Transportation CALTRANS • SURVEYS MANUAL 15-3 TERRESTRIAL LASER SCANNING SPECIFICATIONS • June 2018 This Page Left Intentionally Blank © 2018 California Department of Transportation CALTRANS • SURVEYS MANUAL 15-4 TERRESTRIAL LASER SCANNING SPECIFICATIONS • June 2018 15.1 Stationary Terrestrial Laser Stationary Terrestrial Laser Scanning (STLS) refers to laser scanning applications that are performed from a static vantage point on the surface of the earth. The raw data product of a laser scan survey is a point cloud. When the scanning control points are georeferenced to a known coordinate system, the entire point cloud can be oriented to the same coordinate system. All points within the point cloud have X, Y, and Z coordinates and Laser Return Intensity values (XYZI). The points may be in an XYZIRGB (X, Y, Z coordinates, return Intensity, and Red, Green, Blue color values) if image overlay data is available. The positional error of any point in a point cloud is equal to the accumulation of the errors of the scanning control and errors in the individual point measurements. Just as with reflectorless total stations, laser scan measurements that are perpendicular to a surface will produce better accuracies than those with a large angle of incidence to the surface. The larger the incidence angle (see Figure 15-1), the more the beam can elongate, producing errors in the distance returned. Data points will also become more widely spaced as distance from the scanner increases and less laser energy is returned. At a certain distance the error will exceed standards and beyond that no data will be returned. Atmospheric factors such as heat radiation, rain, dust, and fog will also limit scanner effective range. For in-depth discussions of stationary laser scanning, see the AHMCT Research Center reports “Creating Standards and Specifications for the Use of Laser Scanning in Caltrans 2 Projects” and “Accelerated Project Delivery: Case Studies and Field Use of 3D Terrestrial 3 Laser Scanning in Caltrans Projects: Phase I - Training and Materials.” 2 http://ahmct.ucdavis.edu/pdf/UCD-ARR-07-06-30-01-B.pdf 3 http://ahmct.ucdavis.edu/pdf/UCD-ARR-09-02-28-02.pdf © 2018 California Department of Transportation CALTRANS • SURVEYS MANUAL 15-5 TERRESTRIAL LASER SCANNING SPECIFICATIONS • June 2018 This Page Left Intentionally Blank © 2018 California Department of Transportation CALTRANS • SURVEYS MANUAL 15-6 TERRESTRIAL LASER SCANNING SPECIFICATIONS • June 2018 15.2 STLS Applications Two types of Terrestrial Laser Scanning (TLS) specification groups have been described to differentiate between TLS surveys have varying accuracy, control, and range requirements. “Type A” TLS surveys are hard surface topographic surveys with data collected at engineering-level accuracy. “Type B” TLS surveys are topographic surveys with data collected at lower-level accuracy. See CSM Chapter 11, “Engineering Surveys,” 4 for tolerances and accuracy standards for types of surveys. 15.2-1 Type A - Hard surface topographic surveys: •